28 BOTANICAL GAZETTE. 



Or you may take the ordinary glass slide and fas* en on to it by ma- 

 rine glue, the rubber, glass, block tin or other cell of any desired 

 depth. Any ordinary work on the microscope will give instruclian on 

 the use of tliis or similar cement. Supposing now that the cell is 

 made and fastened to the glass, I then paint a thick coat o( the as- 

 phaltum cement over the whole l)ottom (inside) of the cell so made. 

 This gives you an opaque field. When the object has been properly 

 prepared, by cleansing, I put another coat of the asphaltum on over 

 the first, and on ihis I place the object. There it becomes cemented 

 as the varnish hardens and nothing is left save to put on a cover of 

 the same or nearly the same diameter as the cell, and then lay on 

 over the outer marj^in a ring of asphaltum, zinc or anv suitable ce- 

 ment, wliich excludes the air and fastens the cover. This is all suf- 

 ficiently simple. And it may be well to add that opaque objects are 

 too much neglected because they are not to be used with other than a 

 low power. The smaller lichens may thus be mounted bodily, and 

 so far as their mere external characteristics go, studied more satis- 

 factorily than by any other method. Besides we may then have them 

 safe, handy, and in permanent keeping. Type specimens, if small, 

 should as a rule be so preserved. 



The second class: -objects through which the light is seen, i. e., 

 transparent objects. Some are so thin as to need no sectioning and 

 may, or may not, require the bleaching process described in my pre- 

 vious paper. Suppose they are not so thin! How are i hey to be 

 made so? Evidently by a sharp knife of some foim There are 

 costly instruments of this kind made. Allow me to assure you, the 

 assertion of dealers to the contrary notwithstanding, that you do not 

 need any such knife for any ordinary work. K raz t sharp enough 

 to shave with is the best and handiest instrument you can use. Neither - 

 do you need to have the hol'ow ground out of one surface providing 

 you hold it as you should hold things, i. e., with a firm hand. So 

 then you may well be satisfied with a good razor; providing always 

 thai, it be sharp. Next! How shall the object be held whilst being 

 sectioned? Firs':— it may be held in the hand and if the cuttincr 

 hand be reasonably steady a good section may be secured. Second: 

 — it may be held in an instrument where it is simply screwed fas', and 

 after the first cut gives you a flat surface, by a turn of a screw in the 

 bottom the object thrust forward so thai the next cut shall be of any 

 desired thickness. This is my favorite means of holding the object, 

 and if I have one so small that I cannot so sacuie it, I take a bit of 

 carrot of the proper size, make a slit in this, in wk h I put the minute 

 object; then I screw it and the carrot fast, together. Some use potato 

 as a substitute for the carrot but it is not so good, as the starch grains 

 become separated and adhere to the object giving some trouble to 

 remove them. Other objects too small even for the carrot may be se- 

 cured by making a paper cone of proper diameter to fit the section 

 holder (section cutter as it is called, but this name should Le retained 

 for the knife), then melt paraffine and pour in until you have enough, 

 then in this set your minute objects. Allow the prraffine to harden 

 and with, or without, the paper cone you may screw it into the holder 



